Added links to Windows Vagrant Boxes

The modern.ie team have created a set of Vagrant boxes for Windows XP, Vista, 7, 8, 8.1 which work with Virtual Box. I've added them to this list. The URLs use [aka.ms](https://aka.ms) which is a Microsoft URL shortening site.

Please send any feedback for the boxes to [@IEDevChat](http://twitter.com/IEDevChat).

Currently they do not support OpenSSH or WinRM, but we would like to get your feedback.